OK, this actually works. The nice folks at T-Mobile told me to go to Control Panel...Connections...Internet Accounts...Other, then select GSM only.
This ensures that when the phone logs on after a Network drop, it doesn't automatically connect to GPRS.
However, if you use Picture Messaging, Internet or WAP and they need GPRS, it will connect with no trouble.
I did this and haven't had the fault since.
SE and T_Mobile are finding a long term fix.
Hope this helps
Dave